Re: [AMBER] Question of Parameter Defaults

From: David A Case <>
Date: Sat, 13 Aug 2016 15:48:59 -0400

On Fri, Aug 12, 2016, Robert Molt wrote:
> I am confused on an aspect of parameter values in the GAFF/Amber force
> fields. Using defaults of ff14SB for a molecule I put through
> Antechamber, the frcmod file has the value
> CA-CA-CT-OS 1 0.000 0.000 2.000 same as X
> -c2-c3-X
> for the above dihedral. My understanding is that the order of parameters
> goes dividing factor, k force constant, n periodicity, phi phase angle.

You can find this in $AMBERHOME/dat/leap/parm/gaff.dat, as X-c2-c3-X, along
with a literature reference. Aliphatic torsions are often either very close
to zero, or exactly zero, since there is little intrinsic barrier to rotation.

...hope this helps...dac

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Received on Sat Aug 13 2016 - 13:00:02 PDT
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